Set your tRFC setting to 30 clocks instead of auto or 42-55 clocks as you probably have now and you'll get your latency down another 0.3ns to 51.2ns like mine since at the moment you're a little higher at 51.5ns. My memory doesn't need more voltage to do this so your's shouldn't too (given it's the name Micron chips under the heat spreader no doubt).
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